Up-drawing continuous casting apparatus and up-drawing continuous casting method

ABSTRACT

An up-drawing continuous casting apparatus includes a holding furnace that holds molten metal, a shape determining member that is arranged near a molten metal surface of the molten metal held in the holding furnace, and that determines a sectional shape of a casting by the molten metal passing through the shape determining member, and a cooling portion that cools the molten metal that has passed through the shape determining member. The shape determining member includes, on a main surface on the molten metal surface side, at least one of a protruding portion that protrudes from the main surface, or a recessed portion that is recessed from the main surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an up-drawing continuous casting apparatus and an up-drawing continuous casting method.

2. Description of Related Art

In Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A), the inventors propose a free casting method as a groundbreaking continuous casting method that does not require a mold. As described in JP 2012-61518 A, a starter is first immersed into the surface of molten metal (a molten metal surface), and then when the starter is drawn up, molten metal is also drawn out following the starter by surface tension and the surface film of the molten metal. Here, a casting that has a desired sectional shape is able to be continuously cast by drawing out the molten metal via a shape determining member arranged near the molten metal surface, and cooling it (i.e., the drawn out molten metal).

With a normal continuous casting method, the sectional shape and the shape in the longitudinal direction are both determined by a mold. In particular, the solidified metal (i.e., the casting) must pass through the mold, so the cast casting takes on a shape that extends linearly in the longitudinal direction. In contrast, the shape determining member in the free casting method determines only the sectional shape of the casting, the shape in the longitudinal direction is not determined. Also, the shape determining member is able to move in a direction parallel to the molten metal surface (i.e., horizontally), so castings of various shapes in the longitudinal direction are able to be obtained. For example, JP 2012-61518 A describes a hollow casting (i.e., a pipe) formed in a zigzag shape or a helical shape, not a linear shape in the longitudinal direction.

The inventors discovered that, because the free casting method is an up-drawing continuous casting method, foreign matter (typically referred to as “slag”) such as an oxide that forms on the molten metal surface tends to affect quality.

SUMMARY OF THE INVENTION

The invention thus provides an up-drawing continuous casting apparatus and an up-drawing continuous casting method that inhibits the inclusion of foreign matter in a casting.

A first aspect of the invention relates to an up-drawing continuous casting apparatus. This up-drawing continuous casting apparatus includes a holding furnace that holds molten metal; a shape determining member that is arranged near a molten metal surface of the molten metal held in the holding furnace, and that determines a sectional shape of a casting by the molten metal passing through the shape determining member; and a cooling portion that cools the molten metal that has passed through the shape determining member. The shape determining member includes, on a main surface on the molten metal surface side, at least one of a protruding portion that protrudes from the main surface, or a recessed portion that is recessed from the main surface.

This kind of structure enables foreign matter floating on the molten metal surface to be blocked, such that the inclusion of foreign matter in the casting is able to be effectively inhibited.

The up-drawing continuous casting apparatus according to the aspect described above may also include a molten metal passage portion that is provided in the shape determining member and through which the molten metal passes. The protruding portion may be a first protruding portion that is formed along an edge of the molten metal passage portion.

Also, in the aspect described above, a gap may be provided between the main surface of the shape determining member and the molten metal surface.

As a result, a decrease in the temperature of the molten metal and the incidence of foreign matter on the molten metal surface is able to be inhibited.

Furthermore, in the aspect described above, the shape determining member may have the recessed portion formed at a base of the first protruding portion.

As a result, blocked foreign matter is able to be collected.

Also, in the aspect described above, the protruding portion may include a second protruding portion that is provided on the shape determining member, and that protrudes on a side opposite the molten metal passage portion from a tip end of the first protruding portion.

As a result, the ability to retain blocked foreign matter is increased.

In the aspect described above, the recessed portion may have a triangular sectional shape, and be provided in plurality on the shape determining member.

A second aspect of the invention relates to an up-drawing continuous casting method that uses an up-drawing continuous casting apparatus having a shape determining member that determines a sectional shape of a casting, and a protruding portion or a recessed portion provided on a main surface on a molten metal surface side of the shape determining member, the protruding portion protruding from the main surface and the recessed portion being recessed from the main surface. The up-drawing continuous casting method includes arranging the shape determining member near a molten metal surface of molten metal; passing the molten metal through the shape determining member and drawing up the molten metal; and cooling the molten metal that has passed through the shape determining member and been drawn up.

This kind of structure enables foreign matter floating on the molten metal surface to be blocked, such that the inclusion of foreign matter in the casting is able to be effectively inhibited.

In the aspect described above, the shape determining member may be provided with a molten metal passage portion through which the molten metal passes, and the protruding portion may be a first protruding portion formed along an edge of the molten metal passage portion.

Also, in the aspect described above, a gap may be provided between the main surface of the shape determining member and the molten metal surface.

As a result, a decrease in the temperature of the molten metal and the incidence of foreign matter on the molten metal surface is able to be inhibited.

Moreover, in the aspect described above, the shape determining member may have the recessed portion formed at a base of the first protruding portion.

As a result, blocked foreign matter is able to be collected.

Also, in the example embodiment described above, the shape determining member may be provided with a second protruding portion that protrudes on a side opposite the molten metal passage side from a tip end of the first protruding portion.

As a result, the ability to retain blocked foreign matter is increased.

In the aspect described above, the shape determining member may be provided with a plurality of the recessed members each of which has a triangular sectional shape.

According to the first and second aspects of the invention, it is possible to provide an up-drawing continuous casting apparatus and an up-drawing continuous casting method that inhibits the inclusion of foreign matter in a casting.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a sectional view of a free casting apparatus according to a first example embodiment of the invention;

FIG. 2 is an enlarged sectional view of only an inner shape determining member and an outer shape determining member in FIG. 1;

FIG. 3 is a top view of the inner shape determining member and the outer shape determining member;

FIG. 4 is a bottom view of the inner shape determining member and the outer shape determining member;

FIG. 5 is a sectional view of the inner shape determining member and the outer shape determining member according to a second example embodiment of the invention;

FIG. 6 is an enlarged sectional view of the outer shape determining member encircled by the dotted line in FIG. 5;

FIG. 7 is a modified example of the outer shape determining member shown in FIG. 6;

FIG. 8 is a sectional view of the inner shape determining member and the outer shape determining member according to a third example embodiment of the invention; and

FIG. 9 is an enlarged sectional view of the outer shape determining member encircled by the dotted line in FIG. 8.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, specific example embodiments to which the invention has been applied will be described in detail with reference to the accompanying drawings. However, the invention is not limited to these example embodiments. Also, the description and the drawings are simplified as appropriate to clarify the invention. Terms such as “top-bottom direction” and “left-right direction” and the like match the top-bottom and left-right directions in the drawings.

First Example Embodiment

First, a free casting apparatus (up-drawing continuous casting apparatus) according to a first example embodiment of the invention will be described with reference to FIG. 1. FIG. 1 is a sectional view of the free casting apparatus according to the first example embodiment. As shown in FIG. 1, the free casting apparatus according to the first example embodiment includes a molten metal holding furnace 101, an inner shape determining member 102 a, an outer shape determining member 102 b, support rods 103 and 104, an actuator 105, and a cooling gas nozzle 106.

The molten metal holding furnace 101 holds molten metal M1 such as aluminum or an aluminum alloy, for example, and keeps it at a predetermined temperature. In the example in FIG. 1, molten metal M1 is not replenished into the molten metal holding furnace 101, so the surface of the molten metal M1 (i.e., the molten metal level) drops as casting proceeds. However, molten metal may also be instantly replenished into the molten metal holding furnace 101 during casting such that the molten metal level is kept constant. Naturally, the molten metal M1 may be another metal or alloy other than aluminum.

The inner shape determining member 102 a and the outer shape determining member 102 b are made of ceramic or stainless steel, for example, and are arranged near the molten, metal surface. More specifically, the inner shape determining member 102 a and the outer shape determining member 102 b are arranged such that there is a gap G of approximately 0.5 mm between the molten metal surface and main surface on the lower side (i.e., the molten metal surface side) of each of the inner shape determining member 102 a and the outer shape determining member 102 b. Providing this gap G makes it possible to inhibit the temperature of the molten metal from decreasing as well as inhibit the incidence of slag (foreign matter) M4 on the molten metal surface.

FIG. 2 is an enlarged sectional view of only the inner shape determining member 102 a and the outer shape determining member 102 b in FIG. 1. As shown in FIG. 2, the inner shape determining member 102 a includes a base portion 21 a and a protruding portion 22 a. Here, the protruding portion 22 a that protrudes downward from the base portion 21 a (i.e., from a lower-side main surface of the inner shape determining member 102 a) is formed along an outside edge of the inner shape determining member 102 a. Also, the outer shape determining member 102 b includes a base portion 21 b and a protruding portion 22 b. Here, the protruding portion 22 b that protrudes downward from the base portion 21 b (i.e., from a lower-side main surface of the outer shape determining member 102 b) is formed along an inside edge of the outer shape determining member 102 b.

Moreover, the inner shape determining member 102 a determines the inner shape of a casting M3, and the outer shape determining member 102 b determines the outer shape of the casting M3. The casting M3 shown in FIG. 1 is a hollow casting (i.e., a pipe) with a tube-shaped cross-section in the horizontal direction (hereinafter referred to as “transverse section”). That is, more specifically, the inner shape determining member 102 a determines an inner diameter of the transverse section of the casting M3, and the outer shape determining member 102 b determines an outer diameter of the transverse section of the casting M3.

FIG. 3 is a top view of the inner shape determining member 102 a and the outer shape determining member 102 b. Also, FIG. 4 is a bottom view of the inner shape determining member 102 a and the outer shape determining member 102 b. Here, FIG. 2 corresponds to a sectional view taken along line II-II in FIGS. 3 and 4. As shown in FIGS. 3 and 4, the outer shape determining member 102 b has a rectangular planar shape, for example, and has a circular open portion in the center portion. The inner shape determining member 102 a has a circular planar shape, for example, and is arranged in the center portion of the open portion of the outer shape determining member 102 b. A gap between the inner shape determining member 102 a and the outer shape determining member 102 b is a molten metal passage portion 102 c through which molten metal passes. In this way, the connecting member 102 is formed by the inner shape determining member 102 a, the outer shape determining member 102 b, and the molten metal passage portion 102 c.

As shown in FIG. 4, the protruding portion 22 a is formed along an edge of the inner shape determining member 102 a on a side of the molten metal passage portion 102 c (i.e., an outer edge), on the lower-side main surface of the inner shape determining member 102 a. Also, the protruding portion 22 b is formed along an edge of the outer shape determining member 102 b on a side of the molten metal passage portion 102 c (i.e., an inner edge), on the lower-side main surface of the outer shape determining member 102 b; Here, as shown in FIG. 4, a tip end of each of the protruding portions 22 a and 22 b is immersed in molten metal. Therefore, slag M4 floating on the molten metal surface is able to be blocked by the protruding portions 22 a and 22 b, so the inclusion of the slag M4 in the casting M3 is able to be effectively inhibited.

As shown in FIG. 1, the molten metal M1 is drawn up following the casting M3 by the surface tension and the surface film of the molten metal, and passes through the molten metal passage portion 102 c. Here, the molten metal that is drawn up from the molten metal surface following the casting M3 by the surface film and the surface tension of the molten metal will be referred to as “retained molten metal M2”. Also, the interface between the casting M3 and the retained molten metal M2 is a solidification interface.

The support rod 103 supports the inner shape determining member 102 a and the support rod 104 supports the outer shape determining member 102 b. The positional relationship between the inner shape determining member 102 a and the outer shape determining member 102 b is able to be maintained by these support rods 103 and 104. Also, a gap G is able to be provided by these support rods 103 and 104. Here, having the support rod 103 be a pipe structure, flowing cooling gas through the support rod 103, and moreover, providing blow holes in the inner shape determining member 102 a, enables the casting M3 to be cooled from the inside as well.

The support rods 103 and 104 are both connected to the actuator 105. This actuator 105 enables the support rods 103 and 104 to move in the top-bottom direction (the perpendicular direction) and the left-right direction, while maintaining the positional relationship between the inner shape determining member 102 a and the outer shape determining member 102 b. With this kind of structure, the inner shape determining member 102 a and the outer shape determining member 102 b are able to be moved downward while keeping the gap G at a constant value, as the molten metal level drops as casting proceeds. Also, the inner shape determining member 102 a and the outer shape determining member 102 b are able to be moved horizontally, so the shape of the casting M3 in the longitudinal direction is able to be changed freely.

A cooling gas nozzle (a cooling portion) 106 is used to spray cooling gas (e.g., air, nitrogen, argon, or the like) at the casting M3 to cool the casting M3. The casting M3 is cooled by the cooling gas while being drawn up by a drawer, not shown, that is connected to a starter ST. Accordingly, the retained molten metal M2 near the solidification interface solidifies sequentially, thus forming the casting M3.

Next, the free casting method according to the first example embodiment will be described with reference to FIG. 1. First, the starter ST is lowered so that it passes through the molten metal passage portion 102 c between the inner shape determining member 102 a and the outer shape determining member 102 b, and the tip end of the starter ST is immersed in the molten metal M1.

Next, the starter ST starts to be drawn up at a predetermined speed. Here, when the starter ST separates from the molten metal surface, the retained molten metal M2 that follows the starter ST and is drawn up from the molten metal surface by the surface film and surface tension is formed. As shown in FIG. 1, the retained molten metal M2 is formed in the molten metal passage portion 102 c between the inner shape determining member 102 a and the outer shape determining member 102 b. That is, the inner shape determining member 102 a and the outer shape determining member 102 b give the retained molten metal M2 its shape.

Next, the starter ST is cooled by cooling gas blown from the cooling gas nozzle 106, so the retained molten metal M2 solidifies sequentially from the upper side toward the lower side, thus forming the casting M3. In this way, the casting M3 is able to be continuously cast.

Here, as described above, slag M4 floating on the molten metal surface is able to be blocked before the molten metal M1 passes through the molten metal passage portion 102 c, by the protruding portion 22 a provided on the inner shape determining member 102 a, and the protruding portion 22 b provided on the outer shape determining member 102 b. Therefore, the inclusion of slag M4 in the retained molten metal M2 that has passed through the molten metal passage portion 102 c is able to be inhibited. As a result, the inclusion of slag M4 in the casting M3 is able to be effectively inhibited. Also, the gap G of approximately 0.5 mm is provided between the molten metal surface and the main surfaces on the lower side of the inner shape determining member 102 a and the outer shape determining member 102 b. Therefore, a decrease in the temperature of the molten metal, and the incidence of slag M4 on the molten metal surface are able to be inhibited. Even if the gap G is not provided, the inclusion of the slag M4 in the casting M3 is able to be effectively inhibited by the protruding portion 22 b. Therefore, in the first example embodiment, the gap G is not absolutely necessary.

Second Example Embodiment

Next, a free casting apparatus according to a second example embodiment of the invention will be described with reference to FIG. 5. FIG. 5 is a sectional view of the inner shape determining member 102 a and the outer shape determining member 102 b according to the second example embodiment. The inner shape determining member 102 a and the outer shape determining member 102 b according to the second example embodiment have a more complex structure for blocking the slag M4 than the inner shape determining member 102 a and the outer shape determining member 102 b according to the first example embodiment shown in FIG. 2 do. The other structure is similar to that of the first example embodiment, so a description thereof will be omitted.

FIG. 6 is an enlarged sectional view of the outer shape determining member 102 b encircled by the dotted line in FIG. 5. As shown in FIG. 6, the outer shape determining member 102 b includes a base portion 21 b, a first protruding portion 22 b, a recessed portion 23 b, and a second protruding portion 24 b. Here, the first protruding portion 22 b that protrudes downward from the base portion 21 b is formed along the inside edge of the outer shape determining member 102 b. The recessed portion 23 b is a groove structure formed in the base portion 21 b, at the base of the first protruding portion 22 b, and is formed in an annular shape when viewed in a plan view from below. The second protruding portion 24 b is formed protruding to the outside (i.e., the side opposite the molten metal passage portion 102 c) from the tip end of the first protruding portion 22 b. As shown in FIG. 6, a cross-section of the outer shape determining member 102 b has a hook shape. Naturally, the sectional shape of the recessed portion 23 b is not limited to being rectangular, and may also be another shape such as triangular or semi-circular.

The outer shape determining member 102 b according to the second example embodiment includes the recessed portion 23 b. Therefore, the blocked slag M4 is able to be collected in the recessed portion 23 b, so the inclusion of the slag M4 in the casting M3 is able to be even more effectively inhibited than it is with the outer shape determining member 102 b according to the first example embodiment. Furthermore, the outer shape determining member 102 b according to the second example embodiment includes the second protruding portion 24 b, so the ability of the outer shape determining member 102 b according to the second example embodiment to retain the blocked slag M4 is higher than it is with the outer shape determining member 102 b according to the first example embodiment. As a result, the inclusion of the slag M4 to the casting M3 is able to be even more effectively inhibited. The inner shape determining member 102 a shown in FIG. 5 also has the same structure as the outer shape determining member 102 b, so it displays the same effect.

FIG. 7 is a modified example of the outer shape determining member 102 b shown, in FIG. 6. As shown in FIG. 7, even with a structure in which the second protruding portion 24 b in FIG. 6 is not provided, the blocked slag M4 is able to be collected in the recessed portion 23 b. That is, the inclusion of the slag M4 in the casting M3 is able to be even more effectively inhibited than it is by the outer shape determining member 102 b according to the first example embodiment.

Third Example Embodiment

Next, a free casting apparatus according to a third example embodiment of the invention will be described with reference to FIG. 8. FIG. 8 is a sectional view of the inner shape determining member 102 a and the outer shape determining member 102 b according to the third example embodiment. The inner shape determining member 102 a and the outer shape determining member 102 b according to the third example embodiment have a different structure for blocking the slag M4 than the inner shape determining member 102 a and the outer shape determining member 102 b according to the first example embodiment shown in FIG. 2 do. The other structure is similar to that of the first example embodiment, so a description thereof will be omitted.

FIG. 9 is an enlarged sectional view of the outer shape determining member 102 b encircled by the dotted line in FIG. 8. As shown in FIG. 6, the outer shape determining member 102 b has a base portion 21 b and a plurality of recessed portions 23 b. Here, the plurality of recessed portions 23 b are groove structures formed in a lower-side main surface of the base portion 21 b, and are formed in concentric annular shapes when viewed in a plan view from below. The plurality of recessed portions 23 b all have triangular cross-sections. When the lower-side main surface of the base portion 21 b is a triangular bottom side that forms a cross-section of the recessed portions 23 b, the apex that faces the bottom side is positioned to the inside (i.e., the side with the molten metal passage portion 102 c) of the center of the bottom side on all of the recessed portions 23 b. Also, the height (i.e., the gap G) of the triangular shapes on the top-bottom direction is preferably approximately 0.5 mm. As shown in FIG. 9, the overall cross-section of the outer shape determining member 102 b is saw blade-shaped.

The outer shape determining member 102 b according to the third example embodiment is able to block and collect the slag M4 by the recessed portion 23 b. Here, as described above, by positioning the apex that faces the bottom side of the triangular shape that forms the cross-section of the recessed portion 23 b to the inside of the center of the bottom side, this kind of effect is able to be further improved. Also, by providing a plurality of the recessed portions 23 b, the inclusion of the slag M4 in the casting M3 is able to be even more effectively inhibited. The inner shape determining member 102 a shown in FIG. 8 has the same structure as the outer shape determining member 102 b, and therefore displays the same effect.

As described above, the inner shape determining member 102 a according to the first to the third example embodiments includes at least one of the protruding portion 22 a and a recessed portion (a portion corresponding to the recessed portion 23 b), on the main surface that is on the lower side (i.e. the molten metal surface side), and is thus able to block the slag M4. As a result, the inclusion of the slag M4 in the casting M3 is able to be effectively inhibited. Similarly, the outer shape determining member 102 b according to the first to the third example embodiments includes at least one of the first protruding portion 22 b and the recessed portion 23 b on the main surface on the lower side (i.e., the molten metal side), and is thus able to block the slag M4. As a result, the inclusion of the slag M4 in the casting M3 is able to be effectively inhibited.

In the first to the third example embodiments, a certain effect is able to be obtained when a structure for blocking the slag M4 is provided only on the outer shape determining member 102 b and not on the inner shape determining member 102 a.

The invention is not limited to the example embodiments described above, but may be modified as appropriate. For example, when casting a solid casting instead of the hollow casting illustrated in the example embodiments, only the outer shape determining member 102 b according to the example embodiments need be used, without using the inner shape determining member 102 a. The inclusion of slag (i.e., foreign matter) in the casting is able to be effectively inhibited just as it is in the example embodiments described above. In this case, the open portion provided in the outer shape determining member 102 b serves as the molten metal passage portion 102 c just as it is. 

1. An up-drawing continuous casting apparatus comprising: a holding furnace that holds molten metal; a shape determining member that is arranged near a molten metal surface of the molten metal held in the holding furnace, and that determines a sectional shape of a casting by the molten metal passing through the shape determining member, and a cooling portion that cools the molten metal that has passed through the shape determining member, wherein the shape determining member includes, on a main surface on the molten metal surface side, at least one of a protruding portion that protrudes from the mail surface, or a recessed portion that is recessed from the main surfaces.
 2. The up-drawing continuous casting apparatus according to claim 1, further comprising: a molten metal passage portion that is provided in the shape determining member and through which the molten metal passes, wherein the protruding portion is a first protruding portion that is formed along an edge of the molten metal passage portion.
 3. The up-drawing continuous casting apparatus according to claim 2, wherein a gap is provided between the main surface of the shape determining member and the molten metal surface.
 4. The up-drawing continuous casting apparatus according to claim 2, wherein the shape determining member has the recessed portion formed at a base of the first protruding portion.
 5. The up-drawing continuous casting apparatus according to claim 4, wherein the protruding portion includes a second protruding portion that is provided on the shape determining member, and that protrudes on a side opposite the molten metal passage portion from a tip end of the first protruding portion.
 6. The up-drawing continuous casting apparatus according to claim 1, wherein the recessed portion has a triangular sectional shape, and is provided inplurality on the shape determining member.
 7. The up-drawing continuous casting method that uses an up-drawing continuous casting apparatus having a shape determining member that determines a sectional shape of a casting, and a protruding portion or a recessed portion provided on a main surface on a molten metal surface side of the shape determining member, the protruding portion protruding from the main surface and the recessed portion being recessed from the main surface, the up-drawing continuous casting method comprising: arranging the shape determining member near a molten metal surface of molten metal; passing the molten metal through the shape determining member and drawing up the molten metal; and cooling the molten metal that has passed through the shape determining member and been drawn up.
 8. The up-drawing continuous casting method according to claim 7, wherein the shape determining member is provided with a molten metal passage portion through which the molten metal passes, and the protruding portion is a first protruding portion along an edge of the molten metal passage portion.
 9. The up-drawing continuous casting method according to claim 8, wherein a gap is provided between the main surface of the shape determining member and the molten metal surface.
 10. The up-drawing continuous casting apparatus according to claim 8, wherein the shape determining member has the recessed portion formed at a base of the first protruding portion.
 11. The up-drawing continuous casting method according to claim 10, wherein the shape determining member is provided with a second protruding portion that protrudes on a side opposite the molten metal passage side from a tip end of the first protruding portion.
 12. The up-drawing continuous casting method according to claim 7, wherein the shape determining member is provided with a plurality of the recessed members each of which has a triangular section shape.
 13. The up-drawing continuous casting apparatus according to claim 3, wherein the shape determining member has the recessed portion formed at a base of the first protruding portion.
 14. The up-drawing continuous casting apparatus according to claim 9, wherein the shape determining member has the recessed portion formed at a base of the first protruding portion. 